Bearing processing method, and bearing processing apparatus

ABSTRACT

The processing method of the grooves and the processing apparatus of the present invention do not utilize the elastic deformation of a bearing itself, and by inserting the pin into the cylindrical-shaped core rod which is inserted into the inner circumference of the cylindrical-shaped bearing material, the cylindrical-shaped core rod is depressed against the inner circumference surface of the cylindrical-shaped bearing material and the concavoconvex of the outer circumference of the cylindrical-shaped core rod is transfer-printed on the inner circumference of the cylindrical-shaped bearing material.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority from Japanese Priority Document No. 2003-337405, filed on Sep. 29, 2003 with the Japanese Patent Office, which document is hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a processing method and a processing apparatus of a bearing for supporting a rotating shaft of a motor and the like.

2. Description of the Related Art

At first, a conventional bearing processing method, and a bearing processing apparatus are described with reference to the attached drawings.

FIGS. 4A to 4E show sectional views for describing the conventional bearing processing method and the bearing processing apparatus, and FIG. 5 shows a side view of a forming die used in the conventional bearing processing method for forming grooves on an inner circumference surface of a bearing.

Conventionally, as a processing method of a hydrodynamic bearing for supporting a rotating shaft of a motor, a processing method such as disclosed in Japanese Laid-Open Patent OPH11-190344 has been employed. Hereinafter, this conventional bearing processing method disclosed in FIG. 3 and FIG. 6 of this Japanese Laid-Open Patent OPH11-190344 is described with reference to the attached FIGS. 4A to 4E and FIG. 5.

In the conventional technology disclosed in this Japanese Laid-Open Patent, a cylindrical shaped sintered alloy material (bearing) 1′ is pinched with an upper punch 4 and a lower punch 5 (FIG. 4A), a forming die 3 is inserted in an inner circumference of the sintered alloy material (bearing) 1′ (FIG. 4B), the sintered alloy material (bearing) 1′ is inserted into a die 2 having a smaller diameter than a diameter of the inner circumference of the sintered alloy material (bearing) 1′ (FIG. 4C), while simultaneously pressing the upper punch 4 by a ram 6, convex striations 3 a of the forming die 3 depicted in FIG. 5 are transfer-printed (FIG. 4D), further the sintered alloy material (bearing) 1′ and the die 2 are moved relatively, and the sintered alloy material (bearing) 1′ is taken out (FIG. 4E).

Through the processes as described above, concave grooves corresponding to the convex striations 3 a of the forming die 3 are formed on the inner circumference surface of the sintered alloy material 1′. That is, this conventional fabrication method is a method for transfer-printing the concave grooves on the inner circumference portion of the sintered alloy material 1′ by utilizing elastic deformation of the sintered alloy material 1′.

As described above, the conventional concave groove processing of the inner circumference of the bearing utilizes the elastic deformation of the sintered alloy material 1′, so that there is a defect that a wall-thickness of the sintered alloy material has to be thick enough to show the elastic deformation.

On the contrary, if the wall-thickness of the sintered alloy material 1′ is made thicker, it becomes impossible for the sintered alloy material 1′ to show the elastic deformation, and the convex striations 3 a of the forming die 3 are not able to be transfer-printed.

Further, there is a limit in the elastic deformation of the sintered alloy material 1′, and it is impossible to deform so much. Accordingly, it is only provide concave grooves (depth of the grooves) of around 2 to 4 μm in depth, and this is also a defect that there is no freedom in the depth of the grooves.

When a hydrodynamic bearing is processed by the conventional fabrication method as mentioned above, for example, a ratio of a groove depth to an air gap amount between a rotating shaft and a bearing inner circumference becomes very important, and as the groove depth becomes shallow, the air gap amount has to be managed to be narrower, so that this causes another defect that a machine accuracy has to be more severe and this affects in cost.

As apparent from the above description, the conventional processing method for the inner circumference grooves depends on the elastic deformation of the bearing itself, and the grooves are transfer-printed, so that there is a restriction that the wall-thickness of the bearing has to be thinner, and also there is a defect that the grooves are only transfer-printed in shallow.

Patent Document 1: Japanese Laid-Open Patent OPH-11-190344

SUMMARY OF THE INVENTION

The problems to be solved by the invention is to provide a bearing processing method and a bearing processing apparatus, wherein there is no limitation on wall-thickness of the bearing material, the depth of each groove is deep enough, and the transfer-printing of the concavoconvex is available.

According to the bearing processing method of the present invention, a cylindrical core rod formed with concavoconvex grooves on an outer circumference surface is inserted in a cylindrical-shaped bearing material, and while holding the cylindrical-shaped bearing material and preventing from expanding in the radial direction, a pin is forcedly inserted inside of the cylindrical-shaped core rod as to elastically deform the cylindrical-shaped core rod in the radial direction, so that a bearing is obtained by transfer-printing the convex grooves on the inner circumference surface of the bearing material.

Further, the bearing processing apparatus of the present invention comprises a cylindrical-shaped core rod, while holding a cylindrical bearing material, formed with a predetermined convex groove on an outer circumference surface, a sleeve for preventing the cylindrical-shaped bearing material from expanding in the radial direction, and a pin having a lager diameter than the inside diameter of the cylindrical-shaped core rod and being inserted into a cylinder of the cylindrical-shaped core rod, and the diameter of the cylindrical-shaped core rod is expanded due to the elastic deformation by forcedly inserting the pin into the cylinder, and the bearing is obtained by transfer-printing the convex grooves on the inner circumference surface of the bearing material.

Further, the cylindrical-shaped core rod comprises an integrally formed cylindrical base portion and a major portion, wherein an outside diameter of the base portion is slightly larger than an outside diameter of the cylindrical-shaped bearing material to be attached to the major portion, an outside diameter of the major portion is slightly smaller than an inner circumference diameter of the cylindrical-shaped bearing material, and an inside diameter of the sleeve is slightly larger than the outside diameter of the base portion in the cylindrical-shaped core rod.

The processing method of the grooves and the processing apparatus of the present invention do not utilize the elastic deformation of a bearing itself, and by inserting the pin into the cylindrical-shaped core rod which is inserted into the inner circumference of the cylindrical-shaped bearing material, the cylindrical-shaped core rod is depressed against the inner circumference surface of the cylindrical-shaped bearing material and the concavoconvex of the outer circumference of the cylindrical-shaped core rod is transfer-printed on the inner circumference of the cylindrical-shaped bearing material. Accordingly, there becomes no limitation on the shape of the cylindrical-shaped bearing material, such as the outside diameter of the cylindrical-shaped bearing material, and it is able to adjust a size of the bearing mount portion of the motor and the like, replacement of the bearing, etc. become simple, and the handling thereof becomes easy without requiring a change of design.

Further, according to the present invention, the grooves of the inner circumference in the cylindrical-shaped bearing material are transfer-printed and formed by adopting the elastic deformation of the cylindrical-shaped core rod which is able to simply get a larger elastic deformation than the elastic deformation of the bearing material itself, so that it is able to form deeper grooves on the inner circumference of the cylindrical-shaped bearing material.

The grooves are abele to be formed with fully enough depth, then it becomes possible to easily manage the air gap amount between the shaft and the inner circumference of the bearing, and this can reduce the cost.

By adapting the processing apparatus for the inner circumference grooves of the present invention, a cheap bearing having no limitation on its shape is obtained in comparison with the conventional technology.

The method of the present invention is carried out by inserting a core rod having a slightly smaller outside diameter than an inner circumference diameter of the bearing material and having formed with grooves into the inside of the bearing material, expanding the outside diameter of the cylinder by inserting a pin into the cylinder, and the grooves formed on the outer circumference surface of the cylinder are transfer-printed on the inner circumference surface of the bearing material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side view showing a part of a bearing processing apparatus of the present invention;

FIGS. 2A to 2C are charts for showing a part of process for processing a bearing by applying the bearing processing apparatus of the present invention;

FIGS. 3A and 3B are charts for showing process after the process in FIGS. 2A to 2C;

FIGS. 4A to 4E are sectional views for describing a conventional bearing processing method and processing apparatus; and

FIG. 5 is a sectional view of a forming die for forming grooves on an inner circumference surface of a bearing used in the conventional bearing processing method.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, one of embodiments of a bearing processing method and a bearing processing apparatus of the present invention is described with reference to the attached drawings.

FIG. 1 is a sectional side view showing a part of a bearing processing apparatus of the present invention, FIGS. 2A to 2C are charts for showing a part of process for processing a bearing by applying the bearing processing apparatus of the present invention, and FIGS. 3A and 3B are charts for showing process after the process in FIGS. 2A to 2C.

The bearing processing apparatus of the present invention is described with reference to FIG. 1, at first.

A bearing processing apparatus 10 comprises a core rod 11, a sleeve 12, and a pin 13.

The core rod 11 is a cylindrical-shaped member formed with a hollow tubular portion 11A, and an outside diameter of a base portion 111 is slightly larger than an outside diameter of a later described bearing material 20. Further, an outside diameter of a major portion 112 is formed with a slightly smaller size than an inner circumference diameter of the bearing material 20, and on its outer circumference surface, concave grooves 113 (FIG. 1) for forming grooves 20B (FIG. 1) such as herringbone shaped grooves on the inner circumference surface of the bearing material 20 are formed.

The sleeve 12 is a member serving a roll for protecting for the bearing material 20 to be widened more than necessary, and an inside diameter of the sleeve 12 is slightly larger than the outside diameter in the base portion 111 of the core rod 11, so that the inside diameter makes the base portion 111 to be inserted smoothly. The depth thereof is equal or slightly longer than a length of the core rod 11.

The pin 13 is a cylindrical-shaped member having an acicular apex, and an outside diameter thereof is slightly thicker than an inside diameter in the hollow tubular portion 11A of the core rod 11.

Then, a processing method of the bearing material 20 is described with reference to FIGS. 2A to 2C and FIGS. 3A and 3B.

As shown in FIG. 2A, the cylindrical bearing material 20 and the core rod 11 are prepared, and the major portion 112 of the core rod 11 is inserted inside of the bearing material 20 (FIG. 2B). The major portion 112 is supported by the base portion 111 of the core rod 11, and there is a slight gap between the outer circumference surface of the major portion 112 and the inner circumference surface of the bearing material 20. In addition, the outer circumference surface of the bearing material 20 installed in the major portion 112 of the core rod 11 slightly sets back from the outer circumference surface in the base portion 111 of the core rod 11.

Next, the sleeve 12 is provided as shown in FIG. 2B, and the core rod 11 equipped with the bearing material 20 is inserted inside the sleeve 12 (FIG. 2C). In this case, a slight gap is formed between the outer circumference surface of the bearing material 20 and the inner circumference surface of the sleeve 12.

Then, the pin 13 is provided as shown in FIG. 3A, and the pin 13 is forcedly inserted into the hollow tubular portion 11A of the core rod 11(FIG. 3B). An outer diameter of the pin 13 is thicker than an inside diameter of the hollow tubular portion 11A in the core rod 11, so that the outer circumference surface of the major portion 112 in the core rod 11 expands outwardly by forcedly inserting the pin 13, the inner circumference surface of the bearing material 20 is depressed, and concavoconvex grooves 113 formed on the outer circumference surface of the major portion 112 are transfer-printed.

After that, the pin 13 is removed, the major portion 112 of the core rod 11 is resumed to the original size, and the bearing 20A is taken out. Thus, finished bearing 20A having herringbone shaped grooves 20B around 5 μm in depth is obtained (FIG. 1).

Apparent from the above description, the bearing processing method of the present invention does not utilize the elastic deformation of the bearing itself like conventional technology, but does utilize the elastic deformation of the core rod 11, so that there is little limitation in a wall-thickness of the bearing material 20.

Further, if the core rod 11 itself is formed with a thin wall-thickness or formed with a high elastic material such as a spring steel, a shape memory alloy, and the like, then a large deformation is obtained so that it becomes possible to make the depth of the grooves 20B deeper. If it is able to make the depth of the grooves 20B deeper, it becomes possible to make the air gap amount between the rotating shaft and the bearing inner circumference surface, when the processed bearing 20A is used as a hydrodynamic bearing, so that mechanical accuracy becomes not so severe

As described above, the present invention is described in the case of a motor, for example, however this invention is not limited to a bearing of a motor, but this invention may be adapted to a general rotation device which requires bearings, these may be a rotating shaft of a pump, a drum, a generator, micro-turbine, a micro axle, and the like, and is also adapted in case of processing a bearing for a micro axle. 

1. A bearing processing method comprising the steps of: inserting a cylindrical-shaped core rod having grooves on an outer circumference surface in a cylindrical-shaped bearing material; elastically deforming the cylindrical-shaped core rod in the radial direction by forcedly inserting a pin inside of the cylindrical-shaped core rod while holding the cylindrical-shaped bearing material so as not to expand in the radial direction; and transfer-printing the grooves on the inner circumference surface of the bearing material to form a bearing.
 2. The bearing processing method as cited in claim 1, wherein; said bearing is a hydrodynamic bearing; and said grooves are concave grooves formed on inner circumference surface of the hydrodynamic bearing.
 3. A bearing processing apparatus comprising: a cylindrical-shaped core rod for holding a cylindrical-shaped bearing material and being formed with predetermined grooves on an outer circumference surface; a sleeve for preventing the cylindrical-shaped bearing material from being expanded in the radial direction; and a pin having a lager diameter than the inside diameter of the cylindrical-shaped core rod and being inserted into a cylinder of the cylindrical-shaped core rod, wherein; the diameter of the cylindrical-shaped core rod is expanded due to the elastic deformation by forcedly inserting the pin into the cylinder, and the grooves are transfer-printed on the inner circumference surface of the bearing material to form a bearing.
 4. The bearing processing apparatus as cited in claim 3, wherein; said bearing is a hydrodynamic bearing; and said grooves are concave grooves formed on inner circumference surface of the hydrodynamic bearing.
 5. The bearing processing apparatus as cited in claim 3, wherein; the core rod comprises an integrally formed cylinder-shaped base portion and a major portion; an outside diameter of the base portion is slightly larger than an outside diameter of the cylindrical-shaped bearing material to be attached to the major portion; an outside diameter of the major portion is slightly smaller than an inner circumference diameter of the cylindrical-shaped bearing material; and an inside diameter of the sleeve is slightly larger than the outside diameter of the base portion in the cylindrical-shaped core rod. 